N52 Swap Discussion

[hoveringuy]

It all fits.

The oil pan is very svelte and is equal in height to the subframe, plus with the bevel it probably has more clearance than an original M20. Plus, being fabricated from 14Ga steel it can probably do double-duty as a skid plate.
The shifter is nicely centered, like it was engineered to be that way.
The engine is centered in the bay and lines-up longitudinally with the center of the car.

[hoveringuy]

That's weird, hoveringuy , you're awfully quiet over there.

Yes, I ran out of things to do with the engine hanging from my rafters so I took an hour to install it. Super easy.
The headers clear everything just fine and I probably would have had 1/4" of clearance between #2 and the frame rail even without the relief, but it sure looks cool. I went with 3-bolt flanges instead of V-band and those are nicely accessible. Miles of clearance to the CAB, subframe and sway bar, like OEM.

[hubcapboy]

That's weird, hoveringuy , you're awfully quiet over there.

[hoveringuy]

It looks well done by some PO, but not factory? My 91 318is doesnt have this notch. Anyone else?

Absolutely loving the progress on this, you guys. Its the perfect motor for a 318is :)

Peter

I'll fess-up. I did it.

[Habla]

Are you sure your exhaust won't clear? I checked mine and it's fine. In fact, there's a perfect recess seemingly exactly for the #2 runner.

Maybe it's because I have a facelift car?

*snip*

It looks well done by some PO, but not factory? My 91 318is doesnt have this notch. Anyone else?

Absolutely loving the progress on this, you guys. Its the perfect motor for a 318is :)

Peter

[hoveringuy]

Exhaust update. My headers are almost done, just need to weld the 3-bolt flanges on when I get the secondary done.
No V-bands for me, at least not here. I've always felt that the OBD2 flanges were super-easy to remove and install. V-bands can be king\d of a wrestling match when I've needed to line-up 2 at once.
The reducer isn't just a cone, but has an S-shape. These were fully back-purged, the only place I got sugaring was my tacks.

[hoveringuy]

Are you sure your exhaust won't clear? I checked mine and it's fine. In fact, there's a perfect recess seemingly exactly for the #2 runner.

Maybe it's because I have a facelift car?

[cwlo]

Sorry to see the welding problems. Beg, borrow or steal a Tig. Life would be much easier.

[spiDmang]

Sub'd for an epic build thread!

[hubcapboy]

to get this fit, both of the collectors were cut just behind the cone, and just in front of the factory O2 bungs (which were the wrong type for our O2 sensors anyway), and the front cone has 9 degrees of kick out under the tape to bring it away from the block:



Here's what that looks like from above:



I did NOT think I'd be putting this much effort into the exhaust system...dropping straight down from the 3-to-1 manifolds to a merge would have been waaaaaaaaaay easier, but I'm not planning on making any other performance modifications to the engine, so I guess this is worth it.

[hubcapboy]

Copying a ton of other designs, I'm hoping to bring 2" secondaries back around the transmission like this, with a merge on the diagonal, to a 2.5" single pipe down the center under the drive shaft:


Working from both ends and seeing how much I had to make up in the middle, it looks like if the inboard secondary passes right under the transmission bolt slot, there's just enough room for the other secondary before it hits the radius of the heat shield under the floor pan:



With the dummy block and head transferred over into the engine bay... tragedy once again befell the front bank headers. This is just kissing the inside of the frame rail with the #2 primary:



Dammit. This is forward in the rail from the crossmember, and forward of the front suspension. There's about 1/2" clear between the block and the cylinder 3 primary (you can see that in the photo above) so the current plan is to notch the frame rail and provide clearance with a 2" or 2.5" tube welded in to create room for the sweep. Normally this would be a deal-breaker (I don't love modifying frame rails) but in this case we're in the part of the frame that's already dimpled as crash-absorption. It's only holding the bumper and radiator core in place. I know I'm being stubborn with not modifying other chassis-side components like the sway bar and CABs, but I consider the headers completely optional... you could do this swap with factory north american manifolds and not run into this problem:



Other than that, you can see that it at least looks possible to run the front bank straight under the trans mount rail, with the rear bank kicking out and then turning back to just miss the CAB heat shield:



Before anything else exciting happens on the engine, I expect I'm going to need all of this worked out. For the first start (and until the engine goes in the other car) I can just turn down the last 45 towards the ground. If this doesn't get figured out now my only option is to run the open shorty headers and then try and figure this out when I have a transmission in the way and can't lift the head off (there's NO way these pieces are going to feed in with the engine in place).

[hubcapboy]

My impatience rolled right into the header project, because this is holding up the engine install now that the pan and engine arms are painted. ER308L wire tack welds pretty well with 75/25 gas. I couldn't find any sources that promised me it would, and I don't think I'll be doing more than tacks, but it worked just fine:



Until I went to mount the front bank on my engine and discovered a hopeless interference between the AC lines/compressor and cylinder 1:



This was a real stumper, but the compressor on the S54 shorter and/or further forward, with the lines clocked a little. I totally didn't see this coming. you can see how sharply #1 turns on the AA headers:



for now, I've just cut the #1 primary out to move forward, since I have to clear the engine compartment as well. The straightest part to do that is right here:

[hubcapboy]

I was pretty proud of the work when I started, but as I marked all the leaks, cleaned off the soapy water, got the welder out, patched over them, re-sealed the pressure plate because the welding had burned my sealant, tested it again and found more leaks, ground back enough material because I was too close to the bolts... repeated everything again... it just got uglier and uglier:



That bottom corner? I have to get a bolt in there to mate to a surface that's covered in weld... and it's still leaking. This sat for two weeks while I gritted my teeth and loved my dog, before I finally made it back out to add the last feature I needed, which was the drain for the vapor separator under the intake manifold:



I did as much cleanup as I was ever going to (mostly to make sure I could get bolts in) and soaked the whole thing in a gallon of 30% HCL diluted with "that much" water:



And painted the pan (on the outside) and arms in the dark... in the rain...



This should have been the best looking part of the project... but smearing 6 min epoxy with loose latex gloves and not caring about going back and finishing it or smoothing it... It's pretty globby. I just wanted to move on. On the other hand, I'll be shocked if this leaks, and it'll all be under the engine eventually anyway.

[hubcapboy]

hoveringuy has been quietly pulling ahead but I think he’s saving progress for some big reveal.

I swear I haven’t forgotten about this. I’ve picked up a shop assistant who’s turned out to be kind of a novice:



She's completely useless, and between a few tough weeks at work, loving her super, super hard, and the rain setting in it's been slow going since my last update. BUT here's some new info. the re-design of the starboard engine arm was to accommodate shorty headers. This is vastly overcomplicating the right side of the engine, slowing us down, and creating stress for hoveringuy because as soon as he saw them bolted up he wanted them, but I'm waiting for a second (and third, nando) set of flanges to be cut. Aftermarket headers *are* available for the N52, but I had zero confidence they would fit our chassis, mostly because we have a swaybar behind the crossmember right where all the later models drop their secondaries through. Many people have had success banging e36 headers into our chassis, but they all use "lollipop" CABs to make a little more room, and there's still a lot of swearing apparently.

All of the BMW 6's have a common bore center, so adapting headers from a different engine completely is a solvable problem... but all of the M5x engines have ovalized exhaust ports, so the primary tubes are the wrong shape. The S54, however, has round exhaust ports of a very similar design to the N52, but the flanges are face-mounted (whereas the N52 has a little stub of 40mm exhaust pipe that seats into the head, and forms the "squish seal" with the cone cut into the face of the head). This is a newly cut flange mated to S54 exhaust manifolds (after cutting off the S54 flanges) by way of a short expanded section of 40mm stainless tubing:



With this loosely fit together, and with a 2.5">2" cone taped to the collector, the front bank fits through the engine arm thus:



This was very exciting for everyone nearby, as at least two pairs of these manifolds were available on ebay at the time for less than $75... I don't want to think about what it would cost to have these made. You can see the aluminum tape in the background. This stuff is absolutely incredible for fitting this tubing together. It's sticky, stiff, and you can scratch a little piece out of it to tack weld. While I waited to figure out how to tack weld stainless... I moved back to the pan. Honestly, my mig welding is completely passable for this:



BUT, when subjected to a pressure test... it was absolutely hopeless. I can't stress enough how impossible it is to get rid of pinhole leaks through these little fillet welds. It was a complete nightmare. Steve had gone to extremes to get his to hold pressure overnight, and mine... it was never going to happen. I considered starting the pan over several times, before deciding I was just going to smear epoxy over the welds before painting it. If it leaks, I'll make a new one:

[hoveringuy]

Small update. With no AC compressor the serpentine belt needs to be an exact fit because of the deflection angle of the tensioner. The E90 world has been doing this for a while to cope with AC compressor bearing failures, and the conventional wisdom is to use a Duralast 433K6 belt. I tried that one and it was too long, the only one that works for me is the Duralast 431K6. Effective length 43.1 inches and outside circumference 43.67".